Scientists have developed a speedy way to monitor the effectiveness of cholesterol-reducing statin drugs.
Statins can cut cholesterol levels
By using a high-tech MRI scan they can tell whether the drugs are actually clearing arteries clogged up by fatty plaque deposits.
The technique, developed by Johns Hopkins University, showed how the drugs began to have a significant effect after six months.
The research is published in the journal Circulation.
MRI has been used to monitor blocked arteries before, but it typically took a year or more to produce meaningful results.
The Johns Hopkins team improved their MRI's sensitivity by putting extra coil rings
around the chest of the patients in the study.
An antenna was inserted through the nose and down the oesophagus of each patient to amplify the signal.
The researchers followed 29 patients with clogged arteries - a condition known as atherosclerosis.
Each took a type of statin called simvastatin for three years.
Not only did was their work able to monitor closely the way the drug began to break down deposits, it also provided clues as to how the drug actually works.
The findings suggest statins save lives because they take cholesterol out of the blood, not because of their secondary effects reducing inflammation.
The researchers found that so-called "bad" LDL cholesterol was lowest in patients in whom plaque deposits were reduced the most.
Lead researcher Dr Joao Lima said: "While it has been proven that patients can benefit from even a short period of statin therapy, as early as 16 weeks, our abilities to harness modern technology for monitoring this condition - and tracking the effectiveness of our treatments - have not kept pace until now.
"Our study increases the likelihood that MRI could eventually be used as a predictive technology for determining which patients should be placed on statin therapy for atherosclerosis."
Statins, which were made available over-the-counter in the UK earlier this year, have been shown to be an effective way to cut cholesterol levels, reducing plaque formation by as much as 40%, and death rates by 30%.
But they do not work for everyone, and they are also associated with side effects such as muscle pain, or damage in a small number of cases.
The scans may show whether benefits outweigh risks early in treatment.
Julie Foxton, a senior nurse advisor for the charity Heart UK, told BBC News Online: "This study adds more weight to the fact that statin therapy encourages regression of the atheromatous (unhealthy) plaque and the fact that the effect of this can be seen at an early stage is encouraging for those people who are on statin therapy.
"This study should encourage those people on statin to continue taking their medication as it shows that early intervention is beneficial."